Fuse structures with pin-mounted blade contacts



March 1, 1966 F. J. KOZACKA 3,238,333

MOUNTED BLADE CONTACTS FUSE STRUCTURES WITH PIN 2 Sheets-Sheet 1 Filed Dec. 12, 1961 March 1, 1966 F- J. KOZACKA FUSE STRUCTURES WITH PIN-MOUNTED BLADE CONTACTS Filed Dec. 12, 1961 2 Sheets-Sheet 2 1320832303 Fa' ede2icii! JKozaciia,

ui%8 neg United States Patent 3,238,333 FUSE STRUCTURES WITH PIN-MUUNTED BLADE CONTACTS Frederick J. Kozacka, South Hampton, N.H., assignor to The Chase-Shawmut Company, Newburyport, Mass. Filed Dec. 12, 1961, Ser. No. 158,661 14 Claims. (Cl. 200120) This invention relates to electric fuses, and more particularly to electric fuses comprising blade contacts.

As seen from a more specific point of view this invention relates to electric fuses having a pair of caps, or terminal elements, closing the ends of a tubular casing or fuse tube, and a pair of blade contacts each projecting from the outside of the casing across one of said pair of caps, or terminal elements, into the inside of the casing.

In such structures the blade contacts are preferably mounted on pins projecting transversely through the casing as well as through the blade contacts. Electric fuses comprising pin-mounted blade contacts are disclosed in my United States Patent 2,939,935 Fuse Structures, issued June 7, 1960, and in my United States Patent 3,007,020 Fuse Structures, issued October 31, 1961, and reference may be had to these two patents for further information on fuses having pin-mounted blade contacts.

It is another object of this invention to provide improved fuse structures having pin-mounted blade contacts, and in particular to provide improved fuse structures having pin-mountings for blade contacts of the kind disclosed in the two above referred-to patents.

The dimensional stability of fuses of the aforementioned description depends largely upon the spacing between the points at which the blade contacts project through the caps and are supported by the caps, and the points where the supporting pins project through the blade contacts. If this spacing is relatively narrow, the dimensional stability of the particular design tends to be relatively limited, and if this spacing is relatively wide the dimensional stability of the particular design tends to be high. For this reason, i.e. to impart a reasonably high degree of dimensional stability to fuse structures, the blade contacts thereof should preferably project relatively far into the casing and the points at which the blade contacts are suppored by pins should have a relatively substantial spacing from the points where the blade contacts are supported by the caps.

Meeting the aforementioned requirements with prior art structures, and more particularly with those disclosed in the above referred-to United States Patents 2,939,935 and 3,007,020, results for a given current rating in relatively thin and relatively short fuse links. Such thin fuse links are rather difficult to handle in production, and the relatively small mass thereof is adverse to achieving time delay characteristics in the overcurrent range of the particular fuse.

It is, therefore, another object of the invention to provide electric fuses having a relatively large spacing between the points of support of the blade contacts by the caps, and the points of support of the blade contacts by the supporting pins thereof, and having consequently a relatively high degree of dimensional stability, which fuses are provided with relatively long and thick fuse links for a given current rating, which can be easily handled in production, and tend to achieve relatively long delay times by virtue of the relatively large mass of metal which is involved in them.

Another object of the invention is to provide improved fuses having pinasupported blade contacts. and having overlay means and insulating plates of the kind more fully disclosed in my copending patent application filed November 24, 1958, Ser. No. 775,881 for Fuse Structures.

A further object of the invention is to provide fuses of the kind disclosed in my aforemention patent application having improved means for securing the insulating plates to the fusible element or fuse link.

These and other objects of the invention and advantages thereof will become more apparent from the ensuing description of the invention when read in connection with the accompanying drawings wherein:

FIG. 1 is a longitudinal section of a fuse embodying the present invention taken along 11 of FIG. 2;

FIG. 2 is a section of the same structure as shown in FIG. 1 taken along 22 of FIG. 1;

FIG. 3 is a front view of a pair of fuse links and associated parts adapted to go into the structure shown in FIGS. 1 and 2 instead of the link structure shown in FIGS. 1 and 2; and

FIG. 4 is a side elevation of the structure shown in FIG. 3.

Referring now to the drawings and more particularly to FIGS. 1 and 2 thereof, numeral 1 has been applied to indicate a tubular casing of insulating material, e.g. a melamine-glass-cloth laminate. The ends of casing 1 are closed by caps or terminal elements 2 of metal, and gaskets 3 are interposed between the ends of easing 1 and caps 2. Each cap 2 has a rectangular cut-out 2a having the same geometry as the cross-section of blade contacts 4, and blade contacts 4 project from the outside of casing 1 through the aforementioned cut-outs 2a in caps 2 into the inside of casing 1. Casing 1 accommodates a pair of ribbon fuse links 5 which are submersed in a puverulent fulgurite-forming arc-quenching filler 6 such as, for instance, quartz sand. Fuse links 5 sandwich between the axially outer ends thereof the axially inner ends of blade contacts 4. Reference numeral 7 has been applied to indicate a pair of pins each projecting transversely through casing 1, blade contacts 4, and fuse links 5. Pins 7 are preferably made of spirally wound resilient sheet metal and installed along the lines more fully set forth in the above referred-to United States Patent 3,007,020 to which reference may be had for further details concerning the pin structures 7 as such as well as their integration into the fuse structure. Briefly, sheet metal pins 7 are highly resilient and can readily be compressed radially at certain points thereof and expanded radially at other points thereof. Pins 7 are being compressed radially at the point where they are passed through suitable circular perforations 4a in blade contacts 4, and pins 7 are radially expanded or enlarged at their ends by indentations 2b in caps 2 driven into the ends of pins 2 and operating as pinexpanding wedge means. Other such wedge means, e.g. drive screws, could be substituted for indentations 2b in caps 2, if desired. Reference letter L has been applied to indicate the spacing between the point at which each blade contact 4 is supported by a cap 2 and the point at which each blade contact 4 is supported by a pin 7. This is a minimum distance required to obtain a satisfactory degree of dimensional stability. Fuse links 5 are conductively connectedpreferably by brazing-to blade contacts 4, the points of connection between parts 4 and 5 being designated by the reference character 5a. The spacing between the points 5a of conductive connection between links 5 and blade contacts 4, has been designated by the letter D, and the spacing between blade-contact-mounting-pins 7 has been designated by the letter d. It is apparent that D d. Thus a relatively great length and a relatively large mass of metal for a given current rating can be imparted to links 5. This could not be achieved if D d.

Fuse links 5 are provided with five transverse lines of circular perforations, namely axially outer lines of perforations a, a, center line of perforations c, and two intermediate lines of perforations b, b. Lines of perforations a,

b, c, b, a define five serially related points of minimal cross-sectional area. Links 5 are made of silver or copper and are provided with an overlay 8 of tin immediately adjacent the center line of perforations. Such an overlay has a fusing point which is considerably lower than the fusing point of the base metal, i.e. silver or copper, as the case may be, and severs the base metal by a metallurgical reaction upon reaching its own, relatively low fusing point. Cadmium or indium may be substituted for tin, as is well known in the art, cadmium having a higher fusing point than tin and indium having a lower fusing point than tin. The mass of the overlay 8 has a predetermined heat absorbing capacity. The larger the heat absorbing capacity of the mass of overlay 8, the longer it takes under predetermined overload conditions to heat overlay 8 to the fusing point thereof, the longer the time delay which can be achieved with the particular fuse structure. Additional time delay may be achieved by the addition of two pairs of insulating plates 9 sandwiching the fuse link at the region where the lines b of perforations are located. The theory underlying this additional time delay means has been fully set forth in my above referred-to copending patent application filed November 24, 1958, Ser. No. 775,881 for Fuse Structures, now US. Patent 3,020,372 issued February 6, 1962, and reference may be had to this application for the details of this theory. Plates 9 are preferably made of a suitable synthetic-resin-glass-cloth laminate, such as a melamineglass-cloth laminate. The mode in which plates 9 are attached, or afiixed, to fuse links 5 is of considerable importance. It is preferable to use metallic fasteners for that purpose, but the amount of metal involved and the number of fasteners required must be minimized. The fasteners must not necessarily establish a rigid connection between the fuse links 5 and the plates 9, but relative shifting of parts 5 and 9 must be kept to a predetermined minimum. The aforementioned requirements can be met by providing fasteners which project through one of the perforations in lines b of perforations as well as through plates 9. The outer diameter of such fasteners, and the cross-sectional area thereof, should be substantially less than the diameter and area of the perforations in links 5 through which they pass. Thus one single small eyelet 110 can be used for attaching one pair of plates 9 to one of links 5. Because of their restricted diameter eyelets and plates 9 have a limited freedom of motion in any direction within the planes defined by links 5, but their freedom of motion is sufficiently limited by the edges of the circular perforations in links 5 through which the eyelets 10 project. Thus the maximum lateral motion of each of the pairs of plates 9 is less than the diameter of the perforation through which its supporting eyelet 10 projects, and such a limited lateral displacement of plates 10 is generally acceptable.

All lines a, b, c, b, a of perforations can be produced by one single stamping operation. The axially outer lines a of perforations provide the perforations required for passing pins 7 through the planes defined by links 5. Each fuse link 5 forms two angular bends 5b situated between the points of support 2a of blade contacts 4 by caps 2 and the points of support of blade contacts 4 by pins 7. These bends 5b tend to impart a certain flexibility to fuse links 5, and to preclude damage thereof on account of mechanical shocks to which the fuse structure may be subjected. Each fuse link 5 comprises a portion which overlaps a portion of blade contacts 4 and which is spaced from blade contacts 4, and it is this particular portion of links 5 through which pins 7 project. The outer diameter of pins 7 in the region of fuse links 5 is less than the diameter of the perforations in links 5 through which pins 7 project. Thus there is a clearance left between pins 7 and fuse links 5 preventing the axially outer ends of links 5 immediately adjacent the bends 5b from being shunted-out and short-circuited by pins 7 and caps 2. If such shunting-out and short-circuiting occurred, the effective length of the fuse links 5 would be reduced and the objects of this invention not achieved. A clearance of of an inch has been found to be generally satisfactory between the links 5 and the bladesupporting pins 7, but the above clearance may be increased or decreased, depending upon the requirements of any particular case.

Rivets or other upset fastener means might be substituted for eyelets 10, though eyelets 10 are generally preferable as supporting means for plates 9 since they combine the property of relatively small mass with that of relatively high mechanical strength, particularly shearing strength.

If desired the number of perforations in each line a, b, c, b, a of perforations may be increased, or decreased, to fully meet existing requirements. In some instances one single perforation per line a, b, c, b, a may sufiice.

In FIGS. 3 and 4 like parts as in FIGS. 1 and 2 have been designated by the same reference characters, hoW- ever, with a prime sign added. Thus reference character 4' has been applied to indicate a pair of spaced blade contacts the axially inner ends of which are sandwiched between a pair of ribbon type fuse links 5 of silver or copper. Fuse links 5' are provided with five transverse lines of perforations a, b, c, b, a. Pins 7 project transversely through blade contacts 4', and through circular perforations pertaining to the axially outer transverse lines a of perforations. The transverse center line 0' of perforations is associated with an overlay 8 of tin or a like link-severing lowfusing point metal. Reference numerals 9 have been applied to designate a pair of plates of insulating material, preferably melamine-glasscloth laminate, which are U-shaped and of which each each comprises a web portion and a pair of flange portions. Plates 9 are affixed in such a way to links 5' that they expose the center line c of perforations to the action of the surrounding pulverulent arc-extinguishing filler, preferably quartz sand, not shown in FIGS. 3 and 4, but keep such a filler away from the area, or region, of the two transverse lines b, b of perforations. Eyelets 10' project through plates 10 and through some of the constituent perforations of the lines b of perforations. The edges of the perforations through which eyelets 10 project limit the freedom of motion of plates 9 within the general planes defined by links 5'. The axially outer ends of links 5 are conductively connected to blade contacts 5', preferably by brazed joints indicated by reference character 5a. Links 5' form angular flexible bends 5b situated between brazed joints 5a and pins 7.

When fuses embodying this invention carry their rated current, or a relatively small overcurrent, the highest temperature prevails at the point of narrowest cross-section defined by the three perforations in line 0 of links 5 of FIG. 1. A break is formed at this point shortly upon fusing of overlay 8. Interruption of relatively small overcurrrents is effected by one single break in the center of each of the links 5 and the arc voltage required to interrupt such overcurrents is obtained by progressive back-burning of links 5. Fusion of overlay 8 is delayed by the relative great lengths and masses of links 5, and the presence of plates 9, as more fully explained in my above referred-to copending patent application Ser. No. 775,881. On occurence of major faults the points of narrowest cross-section of links 5 defined by the perforations in lines b, c, b form virtually simultaneously serially related arc gaps Plates 9 keep the fulguriteforming quartz sand 6 substantially away from the breaks covered by plates 9, thus precluding the formation of fulgurites shunting these two breaks and stabilizing the arc voltage, as more fully set forth in United States Patent 2,964,604 to P. C. Jacobs, Jr. et al., issued December 13, 1960, for Current-Limiting Fuses Having Compound Arc-Voltage Generating Means.

it will be apparent from the foregoing that I have provided electric fuses having pin-mounted blade contacts, which fuses combine the features of dimensional stability,

relatively long and relatively thick ribbon fuse links for given current ratings lending themselves to rough handling, and tending to establish considerable time lags in the overcurrent range, which fuses may also include additional means to increase time lag beyond the limits which may be achieved by the presence of relatively large heat absorbing metal masses.

It will be understood that I have described and illustrated in the foregoing preferred embodiments of my invention, and that various alterations and modifications may be made therein without departing from the spirit and scope of the appended claims.

I claim as my invention:

1. An electric fuse comprising in combination:

a tubular casing of insulating material;

a pair of caps closing the ends of said casing, each of said pair of caps including an end plane and a cylindrical lateral surface;

a pair of blade contacts each projecting from the outside of said casing across one of said pair of caps into the inside of said casing;

21 pair of ribbon fuse links inside said casing sandwiching between the axially outer ends thereof the axially inner ends of said pair of blade contacts, said pair of fuse links including portions overlapping said pair of blade contacts and being spaced from said pair of blade contacts;

a plurality of permanent-conductive-connection-establishing means each including an area of conductive connection between one of said axially outer ends of one of said pair of fuse links and one of said axially inner ends of one of said pair of blade contacts;

a pair of bladecontact-mounting-pins each projecting transversely through said casing, one of said pair of blade contacts, and said portions of said pair of fuse links, each of said pair of blade-contact-mountingpins having a larger spacing from said end plane of one of said pair of caps immediately adjacent thereto than the spacing between said end plane of said one of said pair of caps and the immediately adjacent area of conductive connection between one of said axially outer ends of one of said pair of fuse links and one of said am'ally inner ends of said pair of blade contacts.

2. An electric fuse comprising in combination:

- a tubular casing of insulating material;

a pair of caps closing the ends of said casing;

a pair of blade contacts each projecting from the outside of said casing across one of said pair of caps into the inside of said casing;

a pairof ribbon fuse links inside said casing having axially outer ends conductively connected to the axially inner ends of said pair of blade contacts at areas having a predetermined average spacing, said pair of fuse links including portions overlapping said pair of blade contacts and being spaced from said pair of blade contacts; and

a pair of blade-contact-mounting-pins having a spacing between centers less than said predetermined average spacing each projecting transversely through said casing, one of said pair of blade contacts, and said portions of said pair of fuse links.

3. An electric fuse comprising in combination:

a tubular casing of insulating material;

a pair of caps closing the ends of said casing;

a pair of blade contacts each projecting from the out side of said casing across one of said pair of caps into the inside of said casing;

a pair of ribbon fuse links inside said casing sandwiching between the axially outer ends thereof the axially inner ends of said pair of blade contacts, each of said pair of fuse links having a plurality of transverse lines of perforations including a pair of lines of perforations situated adjacent the axially outer ends of each of said pair of fuse links and lying above the axially inner ends of said pair of blade contacts; and

a pair of blade-contact-mounting-pins each projecting transversely through said casing, one of said pair of blade contacts and a perforation in each of said pair of fuse links forming part of one of said pair of lines of perforations adjacent said axially outer ends of each of said pair of fuse links.

4. An electric fuse comprising in combination:

a tubular casing of insulating material;

a cap mounted on each end of said casing;

a blade contact on each end of said casing projecting from the outside of said casing across said cap into the inside of said casing;

ribbon fuse link means inside said casing having ends conducively connected at points relatively close to the immediately adjacent end of said casing to said blade contact on each end of said casing each of said pair of caps including an end plane and a cylindrical lateral surface; and

a blade-contact-mounting-pin on each end of said casing projecting at a point relatively remote from the immediately adjacent end of said casing transversely through said casing, said blade contact on each end of said casing, and said pair of fuse links including portions overlapping said pair of blade contacts and being spaced from said pair of blade contacts, said fuse link means.

5. An electric fuse comprising in combination:

a tubular casing of insulating material;

a pair of caps closing the ends of said casing;

a pair of blade contacts each projecting from the outside of said casing across one of said pair of caps into the inside of said casing;

a pair of blade-contact-mounting-pins each projecting transversely through said casing and through one of said pair of blade contact at first points thereof situated relatively close to the axially inner ends of said pair of blade contacts; and

fuse link means conductively connected to said pair of blade contacts at second points thereof, said second points being situated relatively remote from the axially inner ends of said pair of blade contacts, said fuse link means defining openings for the clear passage of said pair of blade-contact-mounting-pins and said fuse link means including angular bends situated between said first points and said second points.

6. An electric fuse comprising in combination:

a tubular casing of insulating material;

a pulverulent arc-quenching filler inside said casing;

a pair of terminal caps closing the ends of said casing;

ribbon fuse link means conductively interconnecting said pair of terminal caps;

a plurality of transverse lines of spaced perforations extending across said fuse link means and defining points of minimal cross-sectional area;

plate means of insulating material supported by said fuse link means covering the area of some of said plurality of lines of perforations and exposing the area of others of said plurality of lines of perforations to the action of said filler; and

upset fastener means projecting through said plate means and through some of the constituent perforations of said lines for securing said plate means to said fuse link means.

7. An electric fuse comprising in combination:

a tubular casing of insulating material;

a pulverulent arc-quenching filler inside said casing;

a pair of terminal elements closing the ends of said casing;

ribbon fuse link means conductively interconnecting said pair of terminal elements;

a plurality of serially related spaced perforations of predetermined area arranged along said fuse link means, each defining a point of minimal cross-sectional area of said fuse link means;

plate means of insulating material supported by said fuse link means covering the area adjacent some of said plurality of perforations and exposing the area adjacent others of said plurality of perforations to the action of said filler;

and upset fastener means having a substantially smaller cross-sectional area than said predetermined area projecting through said plate means and through some of said plurality of perforations.

8. An electric fuse comprising in combination:

a tubular casing of insulating material;

a pulverulent arc-quenching filler inside said casing;

a pair of terminal caps closing the ends of said casing;

a pair of blade contacts each projecting from the outside of said casing across one of said pair of caps into the inside of said casing;

ribbon fuse link means conductively interconnecting the axially inner ends of said pair of blade contacts;

a plurality of serially related spaced circular perforations of predetermined diameter arranged along said fuse link means each of said plurality of perforations defining a point of minimal cross-sectional area of said fuse link means; plate means of a syntheticresin-glass-cloth laminate sandwiching said fuse link means at points adjacent some of said plurality of perforations and exposing said fuse link means at points adjacent to others of said plurality of perforations to the action of said filler; and

upset fastener means having a cross-section of substantially smaller diameter than said predetermined diameter projecting through said plate means and through some of said plurality of perforations.

9. An electric fuse comprising in combination:

a tubular casing of insulating material;

a pulverulent arc-quenching fulgurite-forming filler inside said casing;

a fusible element in ribbon-form submersed in said filler, said element having a first perforation defining a first zone of minimal cross-sectional area situated between the ends thereof, said element further having additional perforations defining additional zones of minimal cross-sectional area situated between said first zone and said ends of said elements and forming arc gaps upon fusion thereof;

low-fusing-point metal overlay means on said element adjacent said first Zone of minimal cross-sectional area;

plate means of insulating material covering said additional zones of reduced cross-sectional area adapted to preclude upon formation of said are gaps formation of arc-gap-shunting fulgurites by said filler; and

fasteners projecting through said plate means and through said additional perforations for securing said plate means to said element.

10. An electric fuse comprising in combination:

a tubular casing of insulating material;

a filler of quartz sand inside said casing;

a fusible element in ribbon-form submersed in said filler, said element having a center perforation defining a center zone of minimal cross-sectional area, said element further having axially outer perforations defining axially outer zones of minimal cross-sectional area and forming arc gaps upon fusion thereof;

a low fusing point metal overlay on said element adjacent said center zone;

a pair of substantially U-shaped plates of a syntheticresin-glass-cloth laminate sandwic'hing said axially outer zones with the flange portions thereof and exposing between said flange portions thereof said center zone to the action of said filler; and

fastener means projecting through said pair of plates and through said axially outer perforations for securing said pair of plates to said element.

11. An electric fuse comprising in combination:

a tubular casing of insulating material;

a pair of caps closing the ends of said casing;

a pair of blade contacts each projecting from the outside of said casing transversely across one of said pair of caps into the inside of said casing;

a pair of ribbon fuse links inside said casing having axially outer ends conductively connected to the axially inner ends of said pair of blade contacts, each of said pair of fuse links including portions overlapping said pair of blade contacts and being spaced from said pair of blade contacts;

a pulverulent arc-quencing filler inside said casing embedding said pair of fuse links;

axially spaced brazing joints establishing permanent conductive connections between said axially outer ends of said pair of fuse links and said axially inner ends of said pair blade contacts; and

a pair of blade-contact-mounting-pins each projecting transversely through said casing, one of said pair of blade contacts and said portions of said pair of fuse links, each of said pair of pins being supported on both ends thereof by said casing, and the axial spacing between centers of said pair of pins being less than the axial spacing between brazing joints adjacent opposite ends of said pair of fuse links.

12. An electric fuse comprising in combination:

a tubular casing of insulating material;

a pair of blade contacts each projecting from the outside of said casing across one of said pair of caps into the inside of said casing and defining a gap between the axially inner ends thereof;

a pair of ribbon fuse links inside said casing including axially outer portions overlapping and engaging the axially inner ends of said pair of blade contacts, said pair of fuse links further including intermediate portions overlapping and being spaced from said axially inner ends of said pair of blade contacts, and said pair of fuse links further including axially inner portions spanning said gap defined by said axially inner ends of said pair of blade contacts; and

a pair of blade-contact-mounting-pins each projecting transversely through said casing, one of said pair of blade contacts and one of said intermediate portions of said pair of fuse links and each being supported on both ends thereof by said casing.

13. An electric fuse comprising in combination:

a tubular casing of insulating material;

a pair of caps closing the ends of said casing;

a pair of blade contacts each projecting from the outside of said casing across one of said pair of caps into the inside of said casing;

a pair of ribbon fuse links inside said casing sandwiching between the axially outer ends thereof the axially inner ends of said pair of blade contacts, said pair of fuse links including portions overlapping said pair of blade contacts and being spaced from said pair of blade contacts; and

a pair of blade-contact-mounting pins each projecting transversely through said casing, one of said pair of blade contacts and said portions of said pair of fuse links.

14. An electric fuse comprising in combination:

a tubular casing of insulating material;

a pair of caps closing the ends of said casing;

a pair of blade contacts each projecting transversely from the outside of said casing across one of said pair of caps into the inside of said casing;

8,288,383 9 10 a pair of ribbon fuse links inside said casing sandwich- References Cited by the Examiner ing between the axially outer ends thereof the axially UNITED STATES PATENTS inner ends of said pair of blade contacts, said pair of fuse links including portions overlapping said 13:886 7/ 1933 Glowacki 20O 135 pair of blade contacts and being spaced from said 5 1,316,319 9 Niesen 200-132 pair of blade contacts; 1,748,480 2/ 1930 Hooley 200132 conductive means establishing permanent conductive 1,770,196 7/1930 Bussrnan 200135 connections between said axially inner ends of said 2,243,135 5/1941 Triplett 200135 pair of blade contacts and said axially outer ends of 2 316,989 12/ 1957 s d 200-135 Said p offuse links; and 10 2,827,532 3/1958 Kozacka 200-135 a pair of blade-contact-mounting-pins each projecting 2,964,604 12/1960 Jacobs et a1 20 12 transversely through said casing and being supported at opposite ends thereof by said casing, each of said FOREIGN PATENTS pair of blade-contact-mounting-pins further project- 574,023 4/1959 Canada ing transversely through one of said pair of blade 1 contacts and through said pair of fuse links at points BERNARD A GILHEANY, primary Examiner thereof spaced in a direction longitudinally of said pair of fuse links from said conductive means im- SKOLNIK Assistant Examiner mediately adjacent thereto. 

13. AN ELECTRIC FUSE COMPRISING IN COMBINATION: A TUBULAR CASING OF INSULATING MATERIAL; A PAIR OF CAPS CLOSING THE ENDS OF SAID CASING; A PAIR OF BLADE CONTACTS EACH PROJECTING FROM THE OUTSIDE OF SAID CASING ACROSS ONE OF SAID PAIR OF CAPS INTO THE INSIDE OF SAID CASING; A PAIR OF RIBBON FUSE LINKS INSIDE SAID CASING SANDWICHING BETWEEN THE AXIALLY OUTER ENDS THEROF THE AXIALLY INNER ENDS OF SAID PAIR OF BLADE CONTACTS, SAID PAIR OF FUSE LINKS INCLUDING PORTIONS OVERLAPPING SAID PAIR OF BLADE CONTACTS AND BEING SPACED FROM SAID PAIR OF BLADE CONTACTS; AND A PAIR OF BLADE-CONTACT-MOUNTING PINS EACH PROJECTING TRANSVERSELY THROUGH SAID CASING, ONE OF SAID PAIR OF BLADE CONTACTS AND SAID PORTIONS OF SAID PAIR OF FUSE LINKS. 